The present invention provides a process for the production of polyetherester polyols which have hydroxyester groups terminally bound via ester groups to high molecular weight polyether polyol segments. They are produced by first reacting high molecular weight polyoxyalkylene ether polyols (with molecular weights of from about 400 to 10,000, preferably high molecular weight polyoxy-C.sub.2 /C.sub.3 -alkylene ether polyols, and in particular polyoxypropylene ether polyols), with an excess of dicarboxylic acids, dicarboxylic acid anhydrides and/or dicarboxylic acid esters, and reacting the resultant product with an excess of diols to form a polyetherester polyol.
The new, high molecular weight polyetherester polyols thus consist of polyoxyalkylene ether segments.
Moreover, the invention is also directed to the use of the high molecular weight polyetherester polyols in forming polyurethanes, in particular polyurethane elastomers, by using usual further polyurethane starting materials (for example, polyisocyanates and chain extending agents).
Polyether polyols and polyester polyols often cannot be mixed homogeneously with each other and thus can only be used with difficulty as a mixture for polyurethane syntheses.
It has already been attempted according to German Pat. No. 1,940,181 to bind polyether polyols to polyester polyols via diisocyanates, during which polyether-NCO-prepolymers were produced from the polyether diol and excess diisocyanates and these were reacted to form the polyurethane with a polyester diol and optionally other diols.
Another method was proposed in German Offenlegungsschrift No. 2,164,309, in which a polyester containing --CH.sub.2 --CH.R'--OH-end group (R'=H or C.sub.1 -C.sub.6 -alkyl) is heated to high temperatures in the presence of an etherification catalyst, such as H.sub.2 SO.sub.4, whereby an etherification is produced via the terminal hydroxyl groups.
In East German Pat. No. 113,923, polycarboxylic acids are reacted with alkylene oxides in one stage or polycarboxylic acids are reacted with polyether polyols. Also described is a process wherein polyols are first etherified at high temperatures under sulphuric acid catalysis. The resulting mixture is then esterified with dicarboxylic acid (anhydrides). High functional alcohols or carboxylic acids such as glycerin, hexantriol, trimethylol propane, sorbitol, pentaerythrite or benzene tricarboxylic acids are optionally added after etherification to compensate for functionality losses.
According to German Offenlegungsschriften Nos. 2,057,884 and 2,110,278, polyols are produced from polyoxyalkylene polyols, a dibasic carboxylic acid anhydride and an oxiran compound at temperatures of from about 70.degree. to 200.degree. C. and under pressures of up to 3.0 atmospheres excess pressure in a one-stage reaction. Corresponding catalysts must be simultaneously used for reacting the alkylene oxides. By means of this reaction however, no terminal hydroxyester-segmented polyetherester polyols with the desired properties can be formed. Moreover, in most cases the simultaneously used catalysts interfere.
In German Offenlegungsschrift No. 3,201,203, a high molecular weight polyether polyol is reacted with at least one carboxylic acid anhydride (preferably glutaric acid anhydride) to form a carboxylic acid semiester. This semiester is then oxalkylated with at least one alkylene oxide (preferably ethylene oxide) in the presence of at least one thio-dialkylene glycol. This process also necessitates a pressure-oxalkylation reaction and the simultaneous use of interfering thiodihydroxy compounds which have a very unpleasant odor.
According to the present invention, polyetherester polyols are produced according to simple esterification processes and from starting materials which are simple to handle. The resultant polyetherester polyols contain defined hydroxyester segments, which are bound via a further ester group to the polyether polyol. The polyetherester polyols according to the invention are preferably liquid and have a high reactivity (from preferably primary hydroxyl terminal groups) in relation to isocyanates. Moreover, they are free from interfering catalyst residues which show an uncontrolled formation reaction during use as high molecular weight polyhydroxyl compound in the formation of polyurethane plastics materials.